Angiographic imaging including digitally subtracted angiography (DSA) and non-DSA imaging is used in interventional therapy procedures for diagnosis, treatment assessment, and procedure documentation. DSA imaging involves acquiring a reference image (called a mask) which contains only static background detail and is acquired before injection of a contrast agent (e.g., an X-ray opaque dye) into patient anatomy. In order to remove static background detail from images, a mask image is subtracted from subsequent images acquired when a contrast agent is in patient blood which yields a clear picture of blood vessels filled with the contrast agent. Known systems enable a user to review two different multiple frame image sequences by observing them independently simultaneously and synchronously on the same system or multiple different systems. Slight patient movement during the course of a procedure causes mis-alignment between two angiographic images acquired at different times during a procedure using the same imaging system position. Pixel positions in one image do not automatically correlate to the same pixel positions in another image. Also a slight change in the X-ray power values used to acquire the two images affects luminance intensity values obtained. The resultant difference in the display of the two images can lead to incorrect interpretations. Further, comparison of angiographic images usually involves an evaluation of a contrast agent bolus as it travels through the vasculature. In this evaluation, the timing of the contrast agent flow is a clinical parameter that a physician needs observe and understand. Known systems typically are limited to support manual synchronization of the contrast agent flow times of reviewed images.
In an embolization procedure, a treatment is deemed complete when the flow of contrast agent into a portion of imaged anatomy is reduced or eliminated altogether. In some cases, the flow is completely blocked to an area or a specific pathway (e.g., due to a tumor, fibroid, or arteriovenous malformation (AVM) embolization). In this case a user assesses the completion of the procedure by the lack of contrast agent flowing into a specific region. In other cases, a user attempts to partially embolize a portion of the anatomy (e.g. diffuse tumor embolization in the liver, where a proportion of the liver is required to remain viable). For partial embolization procedures a different metric for assessing the completion of the treatment is required that assesses the reduction in the amount of contrast agent in a specific region between two DSA images. A system according to invention principles addresses these requirements and associated problems.